Solar PV modules are well known as devices that convert light energy (electromagnetic radiation) directly into usable electric energy via a photoelectric effect. The process of conversion is well known. Solar PV modules can be formed as mountable panels and in that form, the modules have been installed extensively in the domestic and commercial markets, usually on the roofs of domestic dwellings and commercial buildings, to supplement electricity supply from the normal grid supply, or to feed back into the normal grid supply. PV modules comprise a plurality of PV cells that are connected electrically and physically in various configurations to form the PV module (or ‘solar panel’), while the module also comprises structural support and environmental encapsulation of the PV cells.
To form a PV system for the purpose of electrical energy generation, PV modules are typically installed on mounting structures and electrically interconnected to form PV arrays, along with other balance of system components (BoS) such as inverters, electrical reticulation, switchgear and protection to complete the system.
PV arrays can be designed and constructed in a variety of ways, however common to all PV arrays is the goal of minimising the cost per unit of energy delivered by the PV system. The two main determinants of the cost of energy from a PV system are capital cost and energy generation.
With the exception of the PV modules themselves, the capital cost of a PV array is driven primarily by the cost of materials in the mounting structure (and therefore the complexity of it) and labour requirements for assembly and installation of the PV array.
In contrast, energy generation from a PV system is highly dependent upon the PV array configuration—that is, the 3D spatial orientation of the modules in the PV array. A PV module generates optimal output when it is positioned at an angle which is normal to the incidence of the sun's rays at any given time. Due to the diurnal and seasonal movement of the sun, this results in the modules of a PV array being either mounted on a structure which tracks the path of the sun diurnally and/or seasonally to achieve optimal generation most or all of the time, or otherwise the modules are fixed at a tilt and orientation which in a compromise, nevertheless achieves the maximum possible annual generation without tracking.
PV arrays that are installed to track the path of the sun include dual axis tracking PV arrays (which track diurnally and seasonally) which have the highest capital cost but the highest generation yield, single axis inclined tracking (which track diurnally but not seasonally), and single axis horizontal tracking (which also track diurnally but not seasonally). Non tracking PV arrays are fixed arrays which provide the lowest cost but also lowest energy generation. These include flat arrays, whereby the modules are laid out in a planar configuration and more recently, East-West (EW) PV arrays (which are a subset of fixed PV arrays).
Tracking PV arrays seek to increase the energy yield of a PV array by ensuring the PV modules are orientated as close to an angle normal to the radiation of the sun as possible at any given time. This is achieved by a mechanical (or sometimes hydraulic) mounting structure which moves the PV modules in one or two axis over the course of the sunlight hours.
A fixed PV array currently represents an effective compromise of cost, complexity and operational risk of the PV array with energy generation. In a fixed PV array the PV modules remain fixed for the life of the PV system, therefore an orientation must be chosen which achieves the maximum generation possible from the fixed PV array in the absence of tracking. The orientation of the PV array (including the tilt angle) is often dictated by the structure to which the PV array is fixed. As this is often a roof, often the orientation is not optimal depending on which way the roof faces and the incline of the roof.
An EW configuration essentially splits a planar PV array into two sub-arrays of PV modules, one sub-array orientated towards the east and the other sub-array orientated towards the west. The modules can be arranged in rows, or in end-to-end connection or alignment, with each row arranged as a series of successive triangles each made up of one east-facing and one west-facing module. An EW PV array achieves a capital cost lower than a fixed PV array, due to reduced structural requirements (due to lower wind loadings and more integrated structure), reduced foundation requirements, and reduced array footprint. The downside though is the reduced energy generation due to the non-optimal fixed orientation. Until recently, the cost benefit of the reduced structural requirements did not justify the reduced energy generation, however as PV module cost continues to fall, this balance has changed and in certain applications the EW approach can result in a lower cost of energy than conventional fixed PV arrays.
Given the improving attractiveness of the EW PV array, the present invention is directed to that form of PV array.
Pre-assembled PV arrays have advantages in relation to reduced installation labour and construction timeframe requirements, while portable PV arrays enable use of PV systems in shorter term applications at different locations. Currently, two groups of PV arrays exist that could be described as pre-assembled or portable PV systems.
The first is a collection of low-voltage portable systems designed for use whilst camping, in military exercises, or essentially anywhere where temporary or short term energy generation is required. These systems typically are of small power generation capability, physically small and have the PV modules oriented on a single plane to maximize energy yield (i.e not EW configuration). This group of products is largely irrelevant to the present invention.
The second group of products, which are more relevant to the invention, are larger scale pre-assembled PV arrays that include a folding structure to enable the PV array to be portable. These systems are typically more expensive than a conventional fixed or EW PV array and have PV modules mounted to a complex sub-structure which includes articulated joints for unfolding the array of modules. These systems are planar systems rather than EW systems.
Portable systems of the second group of products are costly and therefore do not provide low cost of energy. They are therefore typically only used in bespoke applications which can justify the added cost necessary to achieve the desired portability of the PV system.
It is the aim of the present invention to provide a portable PV module array that employs an EW PV array in an operational configuration and that has cost and/or installation benefits compared to present portable PV arrays.